Spintronic devices

ABSTRACT

A monolithic reusable microwire assembly can include a substrate and an electrically conductive thin-film wire formed on the substrate. The conductive thin-film wire can include a narrow segment forming an active area. A thermally and electrically insulating barrier can be formed on the electrically conductive thin-film wire. A roughness-reducing layer can be formed on the thermally and electrically insulating barrier and can have minimal surface roughness.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application Ser.No. 62/470,471, filed Mar. 13, 2017, which is incorporated herein byreference.

GOVERNMENT INTEREST

This invention was made with government support under Grant No.DE-SC0000909 awarded by the Department of Energy. The government hascertain rights in the invention.

BACKGROUND

Magnetic resonance of charge carrier (so called polaron) spin states inthin solid films made of π-conjugated polymers can be observed throughthe measurement of charge carrier recombination currents in diodedevices that allow for both electron and hole polaron injection.

Such electrical detection of magnetic resonance (EDMR) is significantlymore sensitive than inductively detected magnetic resonance as theresonantly measured sample current is only weakly dependent of thepolaron ensemble magnetization, and thus, it is not directly dependenton the applied temperature, the magnetic field, or the sample volume.For this reason EDMR on polymer-thin film diodes has been used in thepast for magnetic resonance based absolute magnetometry of mid to lowmagnetic field domains. Furthermore, EDMR spectroscopy at low staticfield B₀ and high driving field B₁ has become of fundamental interestfor the exploration of nonlinear magnetic field phenomena.

SUMMARY

A monolithic reusable microwire assembly can include a substrate and anelectrically conductive thin-film wire formed on the substrate. Theconductive thin-film wire can include a narrow segment forming an activearea. A thermally and electrically insulating barrier can be formed onthe electrically conductive thin-film wire. A roughness-reducing layercan be formed on the thermally and electrically insulating barrier andcan have a surface roughness of less than or equal to 20 nanometers(nm).

A monolithic spintronic device can include a monolithic reusablemicrowire assembly as described herein and a thin-film device formed onthe monolithic reusable microwire assembly and positioned directly abovethe active area of the thin-film wire.

A method of manufacturing a monolithic microwire assembly can includedepositing an electrically conductive thin-film microwire on a substrateand shaping the thin-film microwire to have a narrow segment forming anactive area of the thin-film microwire. The method can also includedepositing an electrical and thermal insulation barrier on the thin-filmmicrowire. A roughness-reducing layer can be deposited on the electricaland thermal insulation barrier to achieve a surface roughness of lessthan 20 nm.

There has thus been outlined, rather broadly, the more importantfeatures of the invention so that the detailed description thereof thatfollows may be better understood, and so that the present contributionto the art may be better appreciated. Other features of the presentinvention will become clearer from the following detailed description ofthe invention, taken with the accompanying drawings and claims, or maybe learned by the practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1 illustrates a cross-sectional view of an example monolithicreusable microwire assembly, in accordance with examples of the presentdisclosure.

FIG. 2 depicts a cross-sectional illustration of a spintronic device, inaccordance with examples of the present disclosure.

FIG. 3A illustrates a vertical stack structure of the layers used tomake up a spintronic device, in accordance with examples of the presentdisclosure.

FIG. 3B depicts top plan view of the device of FIG. 3A, in accordancewith examples of the present disclosure.

FIG. 3C depicts an schematic illustration of an example experimentalmeasurement configuration using a spintronic device of according to FIG.3A, with the resonant driving field B₁ and the Zeeman field of the spinstates B₀ indicated, in accordance with examples of the presentdisclosure.

FIG. 3D is a schematic illustration of a spintronic device havingmultiple thin film devices integrated into a common active area inaccordance with a specific example of the disclosure.

FIG. 4A is a graph of current-voltage characteristics of a spintronicdevice, in accordance with examples of the present disclosure.

FIG. 4B is a graph of magnetoconductivity characteristics with no RFfield (top), and with RF fields of different amplitudes. At the highestdriving fields, a second-harmonic feature appears in the resonancespectrum due to the non-linearity of the RF source, and is of no furtherrelevance.

FIG. 4C is a graph of the linear relation between the peak of theresonance spectrum B₀ ^(c) and the driving frequency, compared to therelation extracted at very low fields for the related polymer materialMEH-PPV.

FIG. 4D is a graph of the low-field magnetic resonance spectrumextracted from the difference between the zero-field and thefinite-field magnetoconductivity curves. The spectrum is accuratelydescribed by the sum (largest peak) of two Gaussian functions (middlepeak, short broad peak) originating from the two hyperfine fielddistributions experienced by the electron and hole spins, respectively.

FIG. 5 is a graph of spectra that are described by a convolution of thetwo Gaussian curves shown in FIG. 4D and a Lorentzian function arisingfrom power broadening. A global fit is used to extract the B₁ strength.

FIG. 6A depicts a change of the spin basis set probed in magneticresonant transitions from the low B₁ field regime to the onset of theregime of the spin-Dicke effect at high resonant driving fields.

FIG. 6B depicts raw data of magnetoconductivity curves as a function ofdriving power at 85 MHz, plotted on a false color scale, showing powerbroadening of the resonance, bleaching and a subsequent inversion ofresonance sign at high driving fields.

FIG. 6C is a plot of the amplitude of the resonance maximum at 3.07 mTas a function of B₁ compared to results obtained with a differentconjugated polymer material, MEH-PPV, in an OLED driven by a coil ratherthan a stripline.

FIG. 7 is a plot of current as a function of voltage for an examplespintronic device.

FIG. 8A is a magnetoresistance graph of current as a function of sweptmagnetic field B₀.

FIG. 8B is a magnetoresistance graph of current difference as a functionof swept magnetic field B₀.

FIG. 8C is a magnetoresistance graph of current difference as a functionof swept magnetic field B₀.

FIG. 8D is a graph of inhomogeneously power-broadened MR line width atvarious power levels which was used to determine magnetic field B₁.

FIG. 9A is a schematic of a magnetometer configuration in accordancewith one example.

FIG. 9B is a plot of observed Bloch Siegert shift using theconfiguration of FIG. 9A. This plot is of raw data ofmagnetoconductivity curves as a function of driving power at 85 MHz,plotted on a false color scale, showing power broadening of theresonance, bleaching and a subsequent inversion of resonance sign athigh driving fields, as well as clearly showing a Block Siegert shiftwhich has not been previously experimentally observed.

FIG. 9C is a plot of current as a function of voltage for the example ofFIG. 9A.

FIG. 9D is a plot of raw data similar to FIG. 9B for the example of FIG.9A.

FIG. 9E is a plot of the amplitude of the resonance maximum at 3.07 mTas a function of B₁ compared to results obtained with a differentconjugated polymer material, MEH-PPV, in an OLED driven by a coil ratherthan a stripline for the example of FIG. 9A.

FIG. 9F is an exploded view of a portion of data from FIG. 9E.

These drawings are provided to illustrate various aspects of theinvention and are not intended to be limiting of the scope in terms ofdimensions, materials, configurations, arrangements or proportionsunless otherwise limited by the claims.

DETAILED DESCRIPTION

While these exemplary embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, it should beunderstood that other embodiments may be realized and that variouschanges to the invention may be made without departing from the spiritand scope of the present invention. Thus, the following more detaileddescription of the embodiments of the present invention is not intendedto limit the scope of the invention, as claimed, but is presented forpurposes of illustration only and not limitation to describe thefeatures and characteristics of the present invention, to set forth thebest mode of operation of the invention, and to sufficiently enable oneskilled in the art to practice the invention. Accordingly, the scope ofthe present invention is to be defined solely by the appended claims.

Definitions

In describing and claiming the present invention, the followingterminology will be used.

The singular forms “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise. Thus, for example, reference to“a particle” includes reference to one or more of such materials andreference to “subjecting” refers to one or more such steps.

As used herein, the term “about” is used to provide flexibility andimprecision associated with a given term, metric or value. The degree offlexibility for a particular variable can be readily determined by oneskilled in the art. However, unless otherwise enunciated, the term“about” generally connotes flexibility of less than 5%, and most oftenless than 1%, and in some cases less than 0.01%.

As used herein with respect to an identified property or circumstance,“substantially” refers to a degree of deviation that is sufficientlysmall so as to not measurably detract from the identified property orcircumstance. The exact degree of deviation allowable may in some casesdepend on the specific context.

As used herein, “adjacent” refers to the proximity of two structures orelements. Particularly, elements that are identified as being “adjacent”may be either abutting or connected. Such elements may also be near orclose to each other without necessarily contacting each other. The exactdegree of proximity may in some cases depend on the specific context.

As used herein, a plurality of items, structural elements, compositionalelements, and/or materials may be presented in a common list forconvenience. However, these lists should be construed as though eachmember of the list is individually identified as a separate and uniquemember. Thus, no individual member of such list should be construed as ade facto equivalent of any other member of the same list solely based ontheir presentation in a common group without indications to thecontrary.

As used herein, the term “at least one of” is intended to be synonymouswith “one or more of” For example, “at least one of A, B and C”explicitly includes only A, only B, only C, and combinations of each.

Concentrations, amounts, and other numerical data may be presentedherein in a range format. It is to be understood that such range formatis used merely for convenience and brevity and should be interpretedflexibly to include not only the numerical values explicitly recited asthe limits of the range, but also to include all the individualnumerical values or sub-ranges encompassed within that range as if eachnumerical value and sub-range is explicitly recited. For example, anumerical range of about 1 to about 4.5 should be interpreted to includenot only the explicitly recited limits of 1 to about 4.5, but also toinclude individual numerals such as 2, 3, 4, and sub-ranges such as 1 to3, 2 to 4, etc. The same principle applies to ranges reciting only onenumerical value, such as “less than about 4.5,” which should beinterpreted to include all of the above-recited values and ranges.Further, such an interpretation should apply regardless of the breadthof the range or the characteristic being described.

Any steps recited in any method or process claims may be executed in anyorder and are not limited to the order presented in the claims.Means-plus-function or step-plus-function limitations will only beemployed where for a specific claim limitation all of the followingconditions are present in that limitation: a) “means for” or “step for”is expressly recited; and b) a corresponding function is expresslyrecited. The structure, material or acts that support the means-plusfunction are expressly recited in the description herein. Accordingly,the scope of the invention should be determined solely by the appendedclaims and their legal equivalents, rather than by the descriptions andexamples given herein.

Spintronic Devices

As previously mentioned, magnetic resonance of charge carrier (polaron)spin states in thin films made of π-conjugated polymers can be observedby measurement of recombination currents in diode devices that allow forboth electron and hole polaron injection. This is referred to aselectrically detected magnetic resonance (EDMR). In contrast toinductively detected magnetic resonance spectroscopy, the sensitivity ofEDMR does not depend on ensemble polarization and thus can be carriedout on very small sample sizes at room temperature and at very lowmagnetic field conditions. These circumstances allow for investigationof very peculiar magnetic resonance parameter domains, including theregime where the amplitude of the resonant driving field B₁ is of thesame order of magnitude as the static magnetic field, B₀. These“non-linear” magnetic resonance conditions are technically hard toachieve for inductively detected magnetic resonance. Additionalbackground details are provided in G. Joshi et al. (2016), Separatinghyperfine from spin-orbit interactions in organic semiconductors bymulti-octave magnetic resonance using coplanar waveguidemicroresonators, Applied Physics Letters 109, 103303, which isincorporated herein by reference.

It is noted that organic light-emitting diodes (OLEDs) make exquisiteprobes to test magnetic resonance phenomena under unconventionalconditions since spin precession controls singlet-triplet transitions ofelectron-hole pairs, which in turn give rise to distinct recombinationcurrents in the conductivity. Magnetic resonance can therefore berecorded in the absence of spin polarization. This characteristic can beexploited to explore the exotic regime of ultrastrong light-mattercoupling, where the Rabi frequency of a charge carrier spin is of orderthe transition frequency of the two-level system. To reach this domain,the Zeeman splitting of the spin states can be lowered, defined by thestatic magnetic field B₀, and the oscillatory driving field of theresonance, B₁, can be raised. This can be achieved by shrinking the OLEDand bringing the source of resonant radio-frequency (RF) radiation asclose as possible to the organic semiconductor in a monolithic devicestructure that incorporates an OLED fabricated directly on top of an RFstripline within one thin-film structure. With driving power of the RFstripline the mW range the regime of bleaching and inversion of themagnetic resonance signal is reached due to the onset of the spin-Dickeeffect, where the individual spin transitions of electron-hole pairsbecome indistinguishable with respect to the driving field andsuperradiance sets in.

The underlying concept of many approaches to quantum informationprocessing by singlet-triplet qubits relies on initialization, control,and readout of the permutation symmetry of a pair of spins. Examples ofthis approach include electrostatically defined coupled quantum dots inGaAs, silicon, or in carbon nanotubes, but also in isolated spins ofunpaired electrons in bulk crystals, the most prominent example beingthe diamond nitrogen-vacancy system. In parallel to these developments,evidence has been emerging that the magnetoceptive abilities of somemigratory avian species also rely on the coherent interconversionbetween singlet and triplet states of photoinduced radical pairs formedin retinal pigment-protein complexes. Such interconversion is driven bylocal hyperfine fields and modified by Earth's static magnetic field. Itappears to be so robust to dephasing influences that it can even beperturbed by the oscillating fields of ambient anthropogenicelectromagnetic noise. OLEDs operate by the electrical injection ofpositive and negative charges and therefore make unique solid-statesystems to study the interconversion of singlet and triplet recombinantcarrier pairs. Such recombination can be detected either inelectroluminescence or in the device current, which has provensufficiently sensitive to monitor even miniscule perturbations in theresonantly controlled nuclear spin ensemble. Nuclear magnetic resonanceimparts perturbations of electronic transport on energy scales as smallas a millionth of kT, but is still resolved in picoampère changes todevice current. The unique appeal of coherent spin electronics in OLEDsis that experiments can, in principle, be carried out at arbitraryresonance frequencies and temperatures. This fact has led to therealization of ultrastrong light-matter coupling in the driving ofsinglet-triplet pair transitions, e.g. the emergence of thenon-perturbative regime of magnetic resonance where the Rabi frequencyapproaches the energetic separation of spin eigenstates. This regime,which leads to the formation of a new singlet-triplet basis of spinwavefunctions, can be analogous to the emergence of superradiantcollectivity of optical dipole transitions in the Dicke effect: When theDC magnetic field B₀ that is applied to the spin ensemble is larger thanthe inhomogeneous broadening and the oscillating driving field B₁exceeds B₀, the individual spins become indistinguishable and interactcollectively with the driving field.

Reaching this unique spin coherence regime necessitates that B₁ becomescomparable to the Zeeman field defining the spin levels, B₀. In somecases, this threshold can be reached by using custom-designed nuclearmagnetic resonance (NMR) coils surrounding the OLED. This “brute force”approach, however, requires extremely high electrical powers, which canlead to excessive heat formation, which can be hard to dissipate and canultimately destroy the OLED. An alternative approach can usesuperconducting stripline resonators to achieve B₁≈B₀. However, thismethod comes with the requirement of low temperatures, where a range ofadditional magnetic resonance features can arise due to long-livedtriplet excitons, and also makes pulsing of the B₁ field prohibitivebecause of the extremely high Q-factors of these resonators. Pulsing ofB₁ is desirable since it allows the detection of coherent Rabi nutationin the device current, which provides an absolute measurement of themagnitude of the local B₁ field acting on the device.

The present disclosure is directed to a new device structure to probethe ultrastrong coupling regime at room temperature by optimizing twoaspects of resonantly driving OLEDs: minimizing field inhomogeneity byshrinking the active device or active site area to a small diameter(e.g. from about 40 μm to about 80 μm, or 57 μm in one specific example)and at the same time optimizing coupling of the B₁ field to the OLED inan architecture combining a stripline RF source and an OLED in onemonolithic thin-film device.

Generally, the spintronic device disclosed herein can include a reusablemonolithic base layer or microwire assembly that can be purposed and/orre-purposed with any suitable organic thin film device fabricated orgrown thereon. By monolithic, it is to be understood that a monolithicassembly or device is formed as a single unitary assembly or device(e.g. layer-by-layer, for example), rather than as separate individualcomponents that are subsequently interconnected or integrated together.The monolithic reusable microwire assembly can include a substrate andan electrically conductive thin-film wire formed on the substrate. Asdescribed above, the conductive thin-film wire can include a narrowsegment forming a narrow active area, which can facilitate roomtemperature measurements with the device. The narrow active area is thusbounded on either end by wider large area thin-film wire portions. Thesewider areas can also aid in heat dissipation and provide larger contactsfor electrical connections. A thermally and electrically insulatingbarrier can be formed on the electrically conductive thin-film wire. Aroughness-reducing layer can be formed on the thermally and electricallyinsulating barrier and can have a surface roughness of less than orequal to 20 nanometers (nm).

One non-limiting example of a monolithic reusable microwire assembly 100is illustrated in FIG. 1. The monolithic microwire assembly 100 caninclude a substrate 102, such as a silicon substrate, quartz substrate,glass, plastic, or other suitable substrate. In some examples, thesubstrate 102 can include or be formed of a material that is suitablefor use as a heat drain for the microwire 110. Accordingly, in someexamples, the substrate 102 can be positioned sufficiently proximate tothe microwire 110 to reasonably function as a heat drain for themicrowire 110. In some additional examples, the substrate 102 is notthermally isolated from the thin-film microwire 110 to allow thesubstrate to function as a heat drain for the microwire 110. Thethickness of the substrate is not particularly limited and can beadjusted as desired. In one non-limiting example, the substrate can havea thickness ranging from about 50 μm to about 2000 μm, and most often100 μm to 500 μm.

In some specific examples, the substrate can include a substrateadhesion layer, or have a substrate adhesion layer formed thereon, tofacilitate adhesion of subsequently formed layers to the substrate. Insome examples, the substrate adhesion layer can also provide electricaland/or thermal insulation, as desired. A variety of suitable substrateadhesion layers can be used. In some examples, the substrate adhesionlayer can include an oxide or nitride dielectric material. In somespecific examples, the substrate adhesion layer can include or be formedof SiO₂. Other materials such as silicon nitride, or metallic adhesionlayers such as Ti, Cr, are also suitable. The substrate adhesion layercan be formed or deposited on the substrate or as part of the substratein a variety of ways, such as by a suitable deposition technique (e.g.PVD, CVD, ALD, the like, or a combination thereof), thermal oxidation,the like, or a combination thereof. The substrate adhesion layer canhave a variety of suitable thicknesses. In one non-limiting example, thesubstrate adhesion layer can have a thickness of from about 20 nm toabout 100 nm. As a general guideline, thinner substrate adhesion layersare desirable.

In some further examples, a diffusion barrier layer 104 can be includedas part of the substrate or deposited on the substrate. The diffusionbarrier layer can be formed of any suitable dielectric material that canact as a diffusion barrier for adjacent layers or materials. In onespecific examples, the diffusion barrier layer can include or be formedof SiN. The diffusion barrier can typically be deposited by chemicalvapor deposition (CVD), physical vapor deposition (PVD), atomic layerdeposition (ALD), the like, or a combination thereof. The diffusionbarrier layer can also typically have any suitable thickness. In onenon-limiting example, the diffusion barrier layer can have a thicknessfrom about 100 nm to about 300 nm, or from about 150 nm to about 250 nm,and in some cases about 150 nm.

In some examples, a thin-film wire adhesion layer 106 can be added tothe substrate 102 or diffusion barrier layer 104 to facilitate adhesionof the thin-film wire 110 to the substrate or intervening layer. In somespecific examples, the thin-film wire adhesion layer can include or beformed of titanium or chromium. The thin-film wire adhesion layer can bedeposited via a variety of deposition techniques. In some examples, thethin-film wire adhesion layer can be deposited by CVD, PVD such assputtering, thermal evaporation, e-beam evaporation, ALD, or the like.This thin-film wire adhesion layer can have any suitable thickness. Inone non-limiting example, the thin-film wire adhesion layer can have athickness of from about 1 nm to about 100 nm, or from about 5 nm toabout 50 nm, or from about 10 nm to about 30 nm. Often, a desiredthickness can depend on a thickness of an adjacent copper top layer. Forexample, thickness can be adjusted based on electrical conductivity ofthe adhesion layer (e.g. which is lower than adjacent copper), in orderto relieve internal mechanical stress, and the like.

The electrically conductive thin-film wire 110 can be deposited on thesubstrate 102, adhesion layer 106, or other intervening layer. Thethin-film wire 110 can be made of a variety of suitable materials, suchas copper, indium tin oxide, gold, niobium, aluminum, tungsten, or othersuitable materials, any metals or superconductors or any conductivematerial. However, it is noted that the thin-film wire typically cannotbe placed in the furnace during manufacture of the monolithic microwire.The thin-film wire can typically be deposited via sputtering,electroplating, electron beam evaporator, thermal evaporator, or thelike. However, other methods of depositing an electrically conductivematerial to form a thin-film microwire can also be used. The thin-filmwire can have a variety of suitable thicknesses. In one non-limitingexample, the thin-film wire can have a thickness from about 700 nm toabout 1400 nm, or from about 800 nm to about 1200 nm, or from about 900nm to about 1100 nm. The thickness can also range from 50 nm to 4microns, where thickness can depend on a desired magnitude of a radiofrequency amplitude, as well as microwire geometry.

In some examples, an additional, or upper, thin-film wire adhesion layer112, such as a titanium adhesion layer, chromium, or other suitableadhesion layer, can be deposited on the thin-wire layer 110. The upperthin-film wire adhesion layer can be deposited via a variety ofdeposition techniques. In some examples, the upper thin-film wireadhesion layer can be deposited by sputtering, thermal or electron beamevaporator, or any other physical vapor deposition techniques, the likeor a combination thereof. In other examples, the upper thin-film wireadhesion layer can be deposited via sputtering, or other PVD techniques.This upper adhesion layer 112 can also have a variety of thicknesses. Inone non-limiting example, the adhesion layer can have a thickness offrom about 0.5 nm to about 20 nm, or from about 1 nm to about 10 nm. Thethickness can generally depend on a thickness of a following top layer.In some examples, the upper thin-film wire adhesion layer can optionallybe oxidized to improve work function and make the active area surfacehydrophilic. This treatment for 1 nm to 4 nm of Ti on gold particularlyimproves the adhesion of gold and PEDOT-PSS that is widely used forfabrication of OLED.

In some further examples, an etch stop layer 114 can be applied to thethin-film wire 110 or upper adhesion layer 112. The etch stop layer caninclude gold, silver or other suitable etch stop material for lateralstructuring. The etch stop layer can be deposited via a variety ofdeposition techniques. In some examples, the thin-film wire adhesionlayer can be deposited by sputtering, evaporators or other PVDtechniques the like or a combination thereof. In other examples, theetch stop layer can be deposited via sputtering, or the like. This layercan have a variety of thicknesses. In one non-limiting example, the etchstop layer can have a thickness from about 1 nm to about 15 nm, fromabout 3 nm to about 10 nm, or from about 5 nm to about 9 nm.

In still further examples, yet another adhesion layer 116, such as atitanium adhesion layer, chromium, or other suitable adhesion layer, canbe applied to the etch stop layer 114. It is also noted that this layercan be oxidized, as desired, to form a titanium oxide layer or othersuitable oxide layer. The adhesion layer can be deposited via a varietyof deposition techniques. In some examples, the adhesion layer can bedeposited by CVD, PVD, ALD, the like or a combination thereof. In otherexamples, the adhesion layer can be deposited via sputtering, or thelike. This adhesion layer 116 can have a variety of thicknesses. In onenon-limiting example, this adhesion layer can have a thickness of fromabout 1 nm to about 25 nm, about 5 nm to about 20 nm, or about 6 nm toabout 10 nm or 15 nm.

A thermally and electrically insulating barrier can be formed on thethin-film wire 110, the adhesion layer 116, or other intervening layer.In some examples, the thermally and electrically insulating barrier canbe formed of one or more layers, such as SiN layer 120 and SiO₂ layer122, for example, or other suitable insulating layer(s) for electricaland thermal insulation such as aluminum oxide and electricallyinsulating oxides. Where an SiN layer 120 is used, the layer can haveany suitable thickness. In one non-limiting examples, the SiN layer 120can have a thickness from about 120 nm to about 250 nm, or from about150 nm to about 200 nm. Where an SiO₂ layer 122 is used, this layer canalso have any suitable thickness. In one specific example, the SiO₂layer 122 can have a thickness from about 500 nm to about 1500 nm, orfrom about 800 nm to about 1200 nm, or from about 900 nm to about 1000nm or 1100 nm. However, it is noted that any suitable number of layerscan be used to form the thermally and electrically insulating layer(s).In some examples, a single thermally and electrically insulating layercan be used. In other examples, two or more thermally and electricallyinsulating layers can be used. It is further noted that, in some cases,some layer(s) can be applied to provide thermal insulation and otherlayer(s) can be applied to provide electrical insulation. The thermallyand electrically insulating barrier can be formed in a variety of ways.For example, the thermally and electrically insulating barrier can bedeposited via a variety of deposition techniques, such as PECVD, PVD,ALD (Al₂O₃), the like or a combination thereof. SiN is particularlyuseful as a diffusion barrier for copper. In addition to its insulatingproperties, SiO₂ acts as the adhesion surface for the next layer, e.g.spin on glass.

A roughness-reducing layer 130 can be deposited on the one or morethermally and electrically insulating layers, such as layers 120 and122. The roughness-reducing layer can be a spin on glass (SOG) layer, aparylene layer, or other suitable layer to decrease the roughness of themonolithic reusable microwire assembly 100. Cured photoresist can alsobe used. The roughness-reducing layer 130 can have any suitablethickness. In one non-limiting example, the roughness-reducing layer canhave a thickness from about 50 nm to about 1500 nm, from about 60 nm toabout 500 nm or 1000 nm, or from 70 nm to about 250 nm. The roughnessreducing layer can provide a low surface roughness to the monolithicmicrowire and associated spintronic device. In some examples, thesurface roughness can be less than 100 nm, less than 50 nm, less than 20nm, less than 10 nm, less than 5 nm, and in some cases less than 1 nm.As used herein, surface roughness generally refers to peak to valleyroughness or vertical displacement as measured by a profilometer. Theroughness-reducing layer can be deposited in a variety of ways. In someexamples, the roughness-reducing layer can be spin-coated on thethermally and electrically insulating barrier. In other examples, theroughness-reducing layer can be deposited via Parylene coater, the like,or a combination thereof. Any suitable deposition technique that canachieve a minimal surface roughness can be employed. Theroughness-reducing layer can provide sufficient smoothness for backelectrical contacts of a subsequently formed thin-film device tominimize or prevent vertical shorts.

In some examples, an intermediary roughness-reducing layer (not shown)can be formed between the thermally and electrically insulating barrierand the roughness-reducing layer to reduce surface roughness prior toapplication of the roughness-reducing layer. For example, surfaceroughness can be reduced to less than or equal to a thickness of the toplayer. As one non-limiting example, a 100 nm SiN layer can be applied tothe thermally and electrically insulating barrier and etched (e.g. viareactive ion etching) to minimize surface roughness of the thermally andelectrically insulating barrier prior to application of theroughness-reducing layer.

It is also noted that the monolithic reusable microwire can be furtheretched to form windows for electrical contacts to the thin-film wire.This can facilitate electrical connections for subsequently formeddevice components.

The monolithic reusable microwire assembly can be used, and subsequentlyre-purposed, with any suitable thin-film device to form a monolithicspintronic device. Generally, a monolithic spintronic device can includea monolithic reusable microwire assembly as described herein and athin-film device formed on the monolithic reusable microwire assembly.The thin-film device can be positioned directly above the active area ofthe thin-film wire of the monolithic reusable microwire assembly.

One specific example of a monolithic spintronic device 200 isillustrated in FIG. 2. It is noted that FIG. 2 illustrates across-sectional view of the monolithic spintronic device within thevertical active area of the device with the thin-film device positioneddirectly above the active area of the thin-film wire. As such,additional lateral features positioned outside of the active area of themonolithic spintronic device are not depicted in this drawing. Infurther detail, the spintronic device can include a monolithic reusablemicrowire assembly including a substrate 202, diffusion barrier layer204, thin-film wire adhesion layer 206, conductive thin-film wire 210,upper thin-film wire adhesion layer 212, etch stop layer 220, etch-stopadhesion layer 220, electrically and thermally insulating layers 220 and222, and roughness-reducing layer 230, as described previously.

An electrical contact layer 240 can be formed on the roughness-reducinglayer 230. The electrical contact layer 240 can be positioned andconfigured to electrically connect with a subsequently formed thin-filmdevice. The electrical contact layer 240 can be formed of any suitableelectrically conductive material. In some specific examples, theelectrical contact layer can be formed of gold, silver, indium,aluminum, niobium, or the like, or a combination thereof. The electricalcontact layer 240 can be deposited or formed in a variety of ways.Typically, the electrical contact layer can be deposited via sputtering.However, other suitable deposition techniques can also be used. Forexample, one simple approach is using silver paint or indium dots. Theelectrical contact layer can have a variety of thicknesses. In someexamples, the electrical contact layer can have a thickness of fromabout 20 nm to about 200 nm, or from about 50 nm to about 100 nm. It isfurther noted that, in some examples, the electrical contact layer 240can also form part of the monolithic reusable microwire assembly.

In some additional examples, an electrical contact adhesion layer 242can be formed or deposited between the roughness-reducing layer 230 andthe etch-stop layer 240. In some specific examples, the electricalcontact adhesion layer 242 can include or be formed of titanium orchromium. The electrical contact adhesion layer 242 can be deposited viaa variety of deposition techniques. In some examples, the electricalcontact adhesion layer can be deposited by CVD PVD, ALD, the like or acombination thereof. In other examples, the electrical contact adhesionlayer can be deposited via sputtering, evaporating and other PVDtechnics or the like. The electrical contact adhesion layer can have anysuitable thickness. In one non-limiting example, the electrical contactadhesion layer can have a thickness of from about 1 nm to about 50 nm,or from about 5 nm to about 20 nm, or from about 8 nm to about 15 nm.

In some further examples, an upper electrical contact adhesion layer 246can be formed or deposited on the electrical contact layer 240. In somespecific examples, the upper electrical contact adhesion layer 246 caninclude or be formed of titanium or chromium. The upper electricalcontact adhesion layer 246 can be deposited via a variety of depositiontechniques. In some examples, the upper electrical contact adhesionlayer can be deposited by CVD, PVD, ALD, the like or a combinationthereof. In other examples, the upper electrical contact adhesion layercan be deposited via sputtering, or the like. The upper electricalcontact adhesion layer can have any suitable thickness. In onenon-limiting example, the upper electrical contact adhesion layer canhave a thickness of from about 0.5 nm to about 50 nm, or from about 1 nmto about 10 nm, or from about 1.5 nm to about 5 nm. It is further notedthat, in some examples, one or more of the electrical contact adhesionlayer 242 and the upper electrical contact adhesion layer 246 can alsoform part of the monolithic reusable microwire assembly.

In the example illustrated in FIG. 2, the thin film device is an organiclight-emitting diode (OLED) formed of two layers 250, 252. Layer 250 isa hole injector layer. The hole injector layer 250 can be formed of avariety of materials suitable for hole injection. One non-limitingexample can include poly(styrene-sulfonate)-dopedpoly(3,4-ethylenedioxythiophene) (PEDOT:PSS). The hole injector layer250 can be spin-coated, or otherwise deposited, on the electricalcontact layer 240, or other intervening layer (e.g. upper electricalcontact adhesion layer 246). The hole injector layer can have a varietyof thicknesses. For example, in some cases, the hole injector layer canhave a thickness of from about 50 nm to about 200 nm, or from about 70nm to about 150 nm, or from about 80 nm to about 120 nm.

Layer 252 is an emitting layer. The emitting layer 252 can be formed ofa variety of materials suitable for light emission. One non-limitingexample can include super-yellow poly(phenylene-vinylene) (SY-PPV).Other organic semiconductors can be used like MEHPPV (partially andfully deuterated), PCBM, P₃HT, Alq₃, PFO and others, also otherinorganic semiconductor. The emitting layer 252 can be spin-coated, orotherwise deposited, on the hole-injection layer 250. The emitting layercan have a variety of thicknesses. For example, in some cases, theemitting layer can have a thickness of from about 50 nm to about 200 nm,or from about 70 nm to about 150 nm, or from about 80 nm to about 120nm.

A cathode can be formed on the OLED thin-film device. The cathode caninclude layers 260, 262, for example. Lower cathode layer 260 canrepresent a calcium layer and upper cathode layer 262 can represent analuminum layer. However, any other suitable cathode materials can beused. For example, LiF and Al also can be used. As a general guideline,the work function of the material should match with the conductionenergy band of the polymer. The cathode layers can be deposited via avariety of techniques. In some examples, the cathode layers can bedeposited by thermal vacuum evaporation, electron beam physical vapordeposition, the like, or a combination thereof. The cathode layers canhave a variety of thicknesses. In some examples, the lower cathode layer260 can have a thickness of from about 0.5 nm to about 50 nm, from about1 nm to about 20 nm, or from about 5 nm to about 10 nm. In someadditional examples, the upper cathode layer 262 can have a thickness offrom about 50 nm to about 500 nm, from about 70 nm to about 250 nm, orfrom about 100 nm to about 200 nm.

An encapsulating film, such as an epoxy or other suitable encapsulatingmaterial, can be used to form an encapsulating layer 270 on the cathode.Spin on glass and high vacuum grease also can be used. The encapsulatinglayer 270 can have any suitable thickness for encapsulating themonolithic spintronic device.

FIG. 3A shows one exemplary spintronic device structure in furtherdetail. The monolithic spintronic device 300 can include a variety oflayers and features, such as those described with respect to FIGS. 1 and2. Specifically, monolithic spintronic device 300 can include asubstrate 302 and a diffusion barrier 304, such as those describedelsewhere herein. The monolithic spintronic device 300 can also includea thin-film microwire 310 deposited on the diffusion barrier layer 304.An etch stop layer 314 can be formed on the thin-film microwire 310. Athermally and electrically insulating barrier 320 can be formed on theetch stop layer 314. A roughness-reducing layer 330 can be formed on thethermally and electrically insulating barrier 320. An electrical contactlayer 340 can be formed on the roughness-reducing layer 330. Aphotoresist layer 348 can be formed on the electrical contact layer 340.An active site 358 can be formed in the photoresist layer 348 within anactive area of the device (i.e. directly above a narrow segment of thethin-film microwire (See FIG. 3B)). The active site 358 can have anarrow diameter D to accommodate a thin-film device within the activesite also having a narrow diameter. In some examples, the diameter D canbe from about 20 μm to about 100 μm, about 30 μm to about 80 μm, orabout 40 μm to about 70 μm. It is noted that, in some examples, thethin-film device can also have a diameter of from about 20 μm to about100 μm, about 30 μm to about 80 μm, or about 40 μm to about 70 μm. Insome specific examples, the thin-film device can have a diameter of fromabout 50 μm to about 60 μm or 65 μm. A thin-film device, such as an OLEDformed of hole injector layer 350 and emitting layer 352, can bedeposited within the active site 358 on the electrical contact layer340. Thus, different metallic, dielectric, and adhesive layers can beused to ensure sufficient electrical and thermal conductivity of the RFstripline (i.e. thin-film microwire), electrical isolation from theOLED, and smoothing of the OLED bottom contact to prevent verticalshorts.

In this particular example, the template structure (i.e the monolithicreusable thin-film microwire assembly) of the device is fabricated up tothe step of the photoresist (PR) layer 348 under cleanroom conditions.The OLED active layers, the hole injector layer 350poly(styrene-sulfonate)-doped poly(3,4-ethylenedioxythiophene)(PEDOT:PSS) and the emitting layer 352 super-yellowpoly(phenylene-vinylene) (SY-PPV) or any other organic semiconductor arespin-coated in a nitrogen-filled glovebox and subsequently contactedwith a cathode layer of calcium and aluminum deposited by thermalevaporation under high vacuum. Material with low magnetic hyperfinefields are particularly useful as it will increase the sensitivity ofmagnetometer as it generate narrower magnetic resonance linewidth.Inorganic semiconductor such as Si can also deposited by sputtering orPECVD or any other deposition technics instead of organic semiconductor.A top plan view of the monolithic spintronic device structure is shownin FIG. 3B. The thin-film wire 310 used to generate the RF radiationruns vertically across the image and is shrunk down to form a narrowsegment 311 having a width W of from about 50 μm to about 300 μm, fromabout 100 μm to about 200 μm, from about 125 μm to about 175 μm, orabout 150 μm, beneath the OLED thin film device 354. The thin-filmmicrowire is electrically and thermally isolated from the OLED by athick thermally and electrically insulating barrier 320 (e.g. layer ofSiO₂), roughness-reducing layer 330 (e.g. spin-on glass (SOG)), andoptional photoresist layer 348 (e.g. for top electrode). The bottomelectrode 340 of the OLED can be made of gold and can protrudeshorizontally to the left of the thin-film microwire 310, as illustratedin FIG. 3B. As illustrated in FIG. 3C, an RF source 390 can be connectedto the thin-film wire 310, generating an oscillating B₁ field 392 in theplane of the OLED. The static magnetic B₀ field 394 can be appliedorthogonally to this field. The direct current flowing through the OLEDcan be measured using an analogue to digital converter (ADC) and a dataacquisition (DAQ) system 380, a transient recorder. In some examples,the system 380 can be connected to the spintronic device 300 via acurrent amplifier 385. The OLEDs are driven in forward bias and thecurrent change under static (B₀) and oscillating (B₁) magnetic field canbe recorded at room temperature.

As will be recognized, these are merely examples of a device that can bemanufactured using the monolithic thin-film microwire described herein.There are numerous other possible thin-film devices, such as OLED, LED(made of semiconductors such as SiC, amorphous Si) devices, that can begrown on top of the monolithic microwire. In another example, a secondthin film microwire device can be deposited on top of and perpendicularto the first microwire having intersecting active areas. Thisconfiguration can be used for RF generation with arbitrary polarizationstates or can provide B₀ modulation and off set fields. Typically, sucha configuration also requires that the magnetic field B₁ for each thinfilm device is equal. This can be accomplished by varying geometryand/or materials according to well-known parameters. For example,besides constituting micron-scale versatile magnetometers, which providean absolute measure of the magnetic field by measuring the resonancefrequency, these monolithic OLED-stripline structures introduced hereoffer versatile structures to easily reach a state of collective spinprecession in OLEDs, in which all spins precess coherently in phase.Since it is the electromagnetic field which induces this coherence, thedemonstration of on-chip pixel-size spin collectivity provides a meansto position multiple individual devices to be driven by the same field.For example, as illustrated in FIG. 3D, a multi-device assembly 301 caninclude multiple thin-film devices 303 within a common active area 305of a conductive thin-film wire 309. The multiple thin-film devices canbe oriented within the narrow segment. The multiple thin-film devicescan be oriented in a one-dimensional series or in multiple layersforming a two or three dimensional array. Furthermore, each thin-filmdevice can include a dedicated electrode 307 and correspondingcounter-electrodes (not shown for clarity). As with other coherentquantum systems such as atomic gases in cavities, it may be possible toentangle the collective Dicke state of one pixel—measured through thedevice current—with that of an adjacent pixel, driven by the same field.Such a manifestation can provide a unique experimental approach toroom-temperature macroscopic coherence phenomena with all the benefitsassociated with the facile tunability of both spin-orbit coupling andhyperfine fields of organic semiconductors. Thus, the devices describedherein can be used in a wide variety of applications, such as for an ACmagnetic field source for organic semiconductor-based monolithicmagnetic resonance magnetometer devices, AC magnetic field source forelectrically detected magnetic resonance spectroscopy, AC magnetic fieldsource for optically detected magnetic resonance spectroscopy, OLED,light emitting diodes, magnetometers, solar cells, resistors,capacitors, and other suitable applications. For example, the devicesdescribed herein can be generally used for magnetometery, EPRspectroscopy, vectorized magnetic field measurements of planetarybodies, and other suitable sensory measurements, such as those describedin U.S. patent application Ser. No. 14/050,605, filed Oct. 10, 2013,which is incorporated herein by reference. Furthermore, devices preparedusing these principles can be formed as absolute magnetic field sensorswhich do not require calibration for accurate measurement of magneticfields or highly scaled micro-electron spin resonance or electricallydetected magnetic resonance spectrometers or other applications whichare based on the application of electromagnetic radiation with very highamplitudes or localized static or quasi-static magnetic fields such aslow-frequency magnetic field modulations.

The present disclosure also describes a method of manufacturing amonolithic thin-film microwire assembly. The method can includedepositing an electrically conductive thin-film microwire on a substrateand shaping the thin-film microwire to have a narrow segment forming anactive area of the thin-film microwire. The method can also includedepositing an electrical and thermal insulation barrier on the thin-filmmicrowire. A roughness-reducing layer can be deposited on the electricaland thermal insulation barrier to achieve a surface roughness of lessthan 20 nm.

Various methods of depositing the different layers of the monolithicthin-film microwire assembly are described elsewhere herein. Shaping thethin-film microwire to have a narrow segment forming an active area ofthe thin-film microwire assembly can be performed in a variety of ways.For example, in some cases, the thin-film microwire can be etched torecess or narrow a portion of the thin-film microwire to have a narrowwidth, such as from about 50 μm to about 300 μm, from about 100 μm toabout 200 μm, from about 125 μm to about 175 μm, or about 150 μm. Thisnarrow segment of the microwire can form an active area of the device.Further, as described herein, the narrow segment can facilitatespintronic measurements at room temperature. In some specific details,the thin-film microwire can be shaped to have a narrow segment viaphotolithography, wet etching, lift-off, the like, or a combinationthereof.

EXAMPLES Example 1—Fabrication of a Spintronic Device

The following example describes the fabrication of monolithiccopper-based lithographically defined wires for broadband (low-Q) EPRexcitation located 1 micron beneath organic light emitting diode (OLED)stacks with a circular surface area of 57 μm diameter that allow forhigh B₁ and low B₀ EDMR spectroscopy. As a brief overview, for thefabrication of these integrated resonator/OLED devices, crossed wireswere deposited on top of a quartz substrate, followed by the depositionof a 1 micron thick dielectric insulator stack below an OLED backcontact. These template structures where brought into an inert gloveboxenvironment where the OLED device layers were deposited.

In further detail, the substrate was selected according to thespectroscopy requirements, for example quartz for simultaneous opticaland electrical magnetic resonance detection and silicon wafer for highpower excitation. The first step is to cover the silicon wafer withoxide layer in a thermal oxidation furnace. The thermal oxidation ofsilicon produces a great insulating layer on silicon wafer. Dry thermaloxidation by diffusion of O₂ gas in Si wafer for 50 nm SiO₂ was obtainedin the furnace at 800° C. to 1000° C. Film thickness was calculatedbased on the interference spectra generated when the light passes thruthe film using NANOSPEC.

A low stress 200 nm SiN film at 800° C. was then deposited on the waferusing Low Pressure Chemical Vapor Deposition (LPCVD). This layer is usedas diffusion barrier for a subsequently formed copper layer. Thethickness of SiN was measured to be 200 nm using NANO SPEC.

Microwire was then deposited via denton sputtering in which Argon plasmaat 3 mTorr detaches particles from a target material for deposition onthe substrate. Denton sputter was used to deposit the following layers:a 20 nm titanium (Ti) adhesion/diffusion barrier, a 1 μm copper (Cu)microwire, a 5 nm Ti adhesion layer, a 5.6 nm gold (Au) etchstopper/electrical contact, and an 8 nm Ti adhesion layer. The thicknessof the microwire was measured using profilometer to be 1 μm.

Photolithography was then performed to further define the microwire.Specifically, a hexamethyldisilazane (HDMS)/xylene (20:80) adhesionpromotor for the photoresist was deposited at 3000 rpm for 60 seconds. Apositive photoresist 1813 was then deposited at 3000 rpm for 60 secondsand soft baked on a hotplate at 110° C. for 1 minute. The wafer wasaligned with the mask using an SUS aligner and exposed to ultravioletradiation for 20 seconds. Subsequently the wafer was dipped into a 1:1AZ developer for 45 seconds, rinsed with deionized water, and driedunder nitrogen. The wafer was post-baked on a hotplate at 100° C. for 2minutes.

The wafer was then cut in half using a programmable silicon dicing saw(Disco DAD641) to achieve clean etching around the microwire. The etchercontainer was placed on top of a hotplate with a temperature sensorinside the container and with a magnetic stir bar rotating at 200 rpm toachieve uniform etching. A buffered oxide etch (BOE) was performed at27° C. for 1 minute. The wafer was then dipped in a commercial Au etchfor 5 seconds. A BOE etch was repeated 27° C. for 40 seconds. The Cu wasthen etched using a chromium etch at 27° C. for 2.5 minutes. After eachstep, the wafer was thoroughly rinsed with deionized water. It is notedthat in some cases residual particles can stick to the surface,especially around the edges of the microwire. Spraying or immersing thewafer in deionized water with agitation for 5 minutes can often helpremove these residual particles. The quality of the etching wasmonitored via optical microscope and profilometer. The photoresist wasremoved using acetone and isopropyl alcohol. Photoresist residuals werethen removed using O₂ plasma at 300 W for 5 minutes.

An insulator layer was then deposited on the microwire by OXFORD Plasma80 Plasma-Enhanced Chemical Vapor Deposition (PECVD), which in this casewas a 175 nm SiN layer as a diffusion barrier for the Cu and a 900 nmSiO₂ layer as an electrical and thermal insulation layer. A 100 nm SiNadded on top for etching can reduce the roughness of the insulatorlayer. Deposition was performed at 300° C. The roughness of theinsulator layer was measured using a profilometer. The 100 nm SiN layerwas etched to reduce surface roughness by Reactive Ion Etching (REI)OSFORD Plasma 80 using CF₄ at 35 sccm and O₂ at 3.5 sccm for 1.9 minutesat 100 W. Surface roughness of the PECVD deposited layer can also bereduced by depositing at a lower temperature (e.g. 100° C.).

The resulting surface roughness was less than 10 nm. To further overcomethe roughness after deposition of the insulator layer, a spin-on-glass(SOG) was applied. Specifically, the SOG layer was passed into a 0.2 mmfilter on the wafer and spin coated at 3000 rpm for 1 minute. The waferwas then placed on a hotplate at 100° C. for 1 minute and then at 200°C. for 1 minute. This process can be repeated to increase the thicknessof the SOG layer and further reduce the roughness of the wafer. Thewafer was then placed in an oven under nitrogen atmosphere at 300° C.for 45 minutes.

Photolithography was again performed to open contact windows to themicrowire. Specifically, a hexamethyldisilazane (HDMS)/xylene (20:80)adhesion promotor for the photoresist was deposited at 3000 rpm for 60seconds. Photoresist 9620 was then deposited at 2000 rpm for 45 secondsand soft baked on a hotplate at 110° C. for 5 minutes and allowing tocool down for 20 minutes. The wafer was aligned with the mask andexposed to ultraviolet radiation for 60 seconds. Subsequently the waferwas dipped into a 1:3 AZ 400 developer to water for 1.5 minutes seconds.

The SOG, SiO₂, SiN, and Ti layers were etched on the windows to provideelectrical contacts for the microwire. Specifically, RIE was performedusing CF₄ at 50 sccm and O₂ at 5 sccm with 100 W forward power for 12minutes. The etching temperature was 15° C. An 8 μm layer of photoresistwas sufficient for masking. The photoresist was removed using acetoneand isopropyl alcohol, followed by subsequent O₂ plasma treatment at 300W for 5 minutes to remove photoresist residuals.

Photolithography was again performed to define the organic lightemitting diodes (OLEDs). Specifically, a hexamethyldisilazane(HDMS)/xylene (20:80) adhesion promotor for the photoresist wasdeposited at 3000 rpm for 60 seconds. A positive photoresist 1813 wasthen deposited at 3000 rpm for 60 seconds and soft baked on a hotplateat 110° C. for 1 minute. The wafer was aligned with the mask and exposedto ultraviolet radiation for 20 seconds. Subsequently the wafer wasdipped into a 1:1 AZ developer for 45 seconds, rinsed with deionizedwater, and dried under nitrogen.

The OLED backcontact electrodes were then deposited using dentonsputting to form the following layers: a 10 nm Ti layer, an 80 nm Aulayer, and a 3.5 nm Ti layer. The wafers were then soaked in acetone fora few minutes, then sonicated for 1.5 minutes, and immediately rinsedwith isopropyl alcohol.

Photolithography was again performed to define the OLED active area.Specifically, a hexamethyldisilazane (HDMS)/xylene (20:80) adhesionpromotor for the photoresist was deposited at 3000 rpm for 60 seconds. Apositive photoresist 1813 was then deposited at 3000 rpm for 60 secondsand soft baked on a hotplate at 110° C. for 1 minute. The wafer wasaligned with the mask and exposed to ultraviolet radiation for 20seconds. Subsequently the wafer was dipped into a 1:1 AZ developer for45 seconds, rinsed with deionized water, and dried under nitrogen. Thewafers were then placed in the oven at 300° C. for 45 minutes. It isnoted that an alternative approach to define the OLED active area caninclude depositing a 120 nm SiN layer via PECVD, and afterphotolithography, etch the SiN layer in the active area and the windowsfor electrical contacts.

O₂ plasma was then used to oxidize the Ti layer to change the workfunction of Ti and use the hydrophilic property of TiO₂ for depositionPEDOT:PSS for the OLED structure. The wafer was covered with photoresist1813 before dicing to keep the active area clean. A programmable silicondicing saw (Disco DAD641) was used to dice the wafer with a 250 mmdicing blade. The photoresist was removed using acetone and isopropylalcohol, as described previously. The active area of the device wasexposed to a UV Ozone Cleaner under O₂ atmosphere for 7 minutes.

PEDOT:PSS was then coated on the structure and subsequently dried on ahotplate at 110° C. for 10 minutes. SY-PPV was then coated and dried ona hotplate at 100° C. for 5 minutes. A 7 nm Ca layer and 150 nm Al layerwere deposited via a glove box evaporator. An encapsulating epoxy layerwas then coated and cured at ambient temperature for 12 hours.

Example 2—Fabrication of Another Spintronic Device

The layer stack developed for the experiments presented in this studyresulted from the requirement to stack organic thin-film devicesdirectly on top of highly conducting RF thin-film wires that can beoperated at room temperature, provide good electrical insulation andthermal isolation to the organic device layers as well as a smoothinterface with a roughness below 10 nm, while, at the same time, providegood heat sinking. To meet all these requirements at the same time istechnologically non-trivial.

Bulk Cu is an excellent room-temperature conductor, but the surface of alayer stack consisting of Cu films with a thickness on the order of amicron and subsequently deposited, equally thick insulating layers istoo rough and thus, unsuitable for the deposition of thin-film organicsemiconductor devices. Thus, in order to smooth out the surfaceroughness and to allow fabrication of organic electronic devices on topof the Cu microwire, a spin-on-glass (SOG) intermediate coating(IC1-200) was used, provided by Futurrex, Inc., which is apolysiloxane-based spin-on dielectric material. In this geometry, adielectric materials stack provides all the heat isolation, electricalinsulation and the mechanical smoothing functions which are needed.

The layer stack, as illustrated in FIGS. 3A-3B, constitutes a system ofsuccessfully deposited thin-film materials, with intermediate lateralstructuring steps which together created a thin-film wire system withthe numerous beneficial properties: The application of AC currents inthe radio-frequency to microwave-frequency range allowed for thegeneration of very homogeneous, high-amplitude in-plane AC magneticfields which were utilized for magnetic resonance application. The thinfilm wire was electrically insulated and thermally isolated from thesurface of the stack system. Heating of the wire during continuousoperation changed only marginally the stack surface as the heat wasdrained through the silicon substrate below the layer stack. The surfaceof the layer stack had very low roughness (few nm range) allowing forthe deposition of the thin-film layers, i.e. the organic semiconductorlayer stacks for bipolar injection device used in the experimentspresented in Example 3.

In order to implement the stack system, the following layer stack wasused:

-   -   Silicon substrate    -   Optional 50 nm SiO₂ layer for substrate adhesion    -   200 nm SiN for electrical insulation and diffusion barrier for        the Cu but not too strong thermal isolation from substrate    -   70 nm Ti for adhesion    -   1μ Cu for the thin-film wire    -   10 nm Ti for adhesion    -   5 nm Au as etch stop for lateral structuring    -   8 nm Ti for adhesion    -   175 nm SiN    -   930 nm SiO₂ for electrical and thermal insulation    -   340 nm Spin-on-glass (930 nm) in order to reduce roughness    -   10 nm Ti for adhesion    -   80 nm Au as back contact for the organic layer stack with        appropriate work function for hole injection. Although Au can be        suitable, Ag or other conductive materials can also be suitable.    -   3 nm Ti for adhesion—due to the very small thickness, the        surface work function was determined by the underlying Au layer.        The Au layer can be optionally surface modified to adhere to        PEDOT OLED layers.

A Heidelberg MicroPG 101 Pattern Generator was used to form the layersand patterns. The mask was developed with developer AZ 1:1 for 45 sec.Mask cleaning took place using spin rinse dryers (SRD). The mask designpattern and sizes were verified by optical microscopy. The mask wasplaced in a chrome etch for 2.5 min, cleaned in DI water for 2 min, andthen cleaned in a SRD. A low stress 200 nm SiN film at 800° C. wasdeposited on (100) surface oriented c-Si wafers wafers using LowPressure Chemical Vapor Deposition (LPCVD). The thickness of SiN wasverified using a NANOSPEC reflectometer.

The following layers were deposited via sputtering using a 3 mTorr Argonplasma:

-   -   Ti 20 nm (adhesion/diffusion barrier)    -   Cu 1 um (microwire)    -   Ti 5 nm (adhesion)    -   Au 6.5 nm (etch stopper/electrical contact)    -   Ti 8 nm (adhesion for next layer)        Photolithography for the definition of the microwire used        HMDS/Xylene (20:80) at 3000 rpm for 60 sec to improve adhesion        of photoresist to surface. A positive photoresist 1813 was        deposited at 3000 rpm for 60 sec followed by soft bake using a        hotplate at 110° C. for 1 min. The wafer was aligned with the        lithography mask and exposed to UV light for 20 sec. The        assembly was dipped into developer Az 1:1 for 45 sec and then        rinsed in DI water, followed by drying with N₂. The assembly was        then post baked on a hotplate at 110° C. for 2 min.

Structuring of the microwire used a wet etch conducted at a wet bench.After each step the wafer was thoroughly rinsed with DI water. Residualparticles that were stuck to the surface, especially around the edges ofmicrowire were flashed off the wafer with a DI water spray. Similarly,immersing the wafer in DI water container with agitation for 5 minhelped to remove residual particles. The etch quality was checked usingan optical microscope and a profilometer. Removal of the photoresisttook place by employment of acetone and isopropanol (IPA), electronicgrade. For the removal of photoresist residuals, an O₂ plasma was used.

Example 3—Evaluation of a Spintronic Device

A spintronic device manufactured according to Example 2 was furthercharacterized. FIG. 4A shows a current-voltage characteristic of thedevice. The OLED current shows the expected diode characteristics,turning on just above a bias of 2 V. At constant voltage, the current ofthe device changes under application of an external magnetic field B₀.The top curve in FIG. 4B shows the magnetoconductivity characteristicsof a device operating at a current of 101 nA. Note that the tick markscorrespond to a current change of 200 pA. The current initiallydecreases slightly with increasing B₀ within the first 0.2 mT from theorigin (the ultrasmall magnetic field effect) and subsequently increasesagain. The lower three curves show the same measurements, offset on thecurrent axis, with oscillating B₁ fields applied at a frequency of 85MHz and amplitudes of 18.5±1.4, 165±2 and 587±7 μT, respectively. The RFfield leads to a dip in the magnetoconductivity curves. This dip resultsfrom the fact that hyperfine fields induce mixing between singlet andtriplet electron-hole pair states in the conjugated polymer, and theexternal magnetic field B₀ tends to suppress this mixing. The externalRF field reopens the mixing channel at the resonant magnetic field,quenching the current. As B₁ increases from 18.5 to 165 μT, theresonance deepens but also broadens. This effect is a consequence ofpower broadening, arising from the fact that the large B₁ amplituderesults in a larger number of individual spins within thehyperfine-broadened ensemble coupling to the oscillatory field. At 587μT, the resonance spectrum is clearly broadened, but the amplitude isalso decreased. This reduction in the resonance amplitude is a signatureof the emergence of ultrastrong coupling, which leads to the formationof a new spin basis set and new transition selection rules. We notethat, in addition to the spin-½ resonance at 3.07 mT (85 MHz), at thehighest driving fields a second-harmonic feature is also observed in thecurrent at 6.14 mT. This second harmonic likely arises from the slightnon-linearity of the RF amplifier, which will lead to a weaksecond-harmonic component in the RF radiation generated in the striplineat the nominal frequency of 85 MHz. We stress that all measurements areof the steady-state current, without the need for modulation or lock-indetection. It is not possible to achieve sufficient RF power in the OLEDin non-monolithic devices to enable direct-current detection.

The resonance feature follows the dependence of position of theresonance peak B₀ ^(c) on driving frequency f expected for a freeelectron, as plotted in FIG. 4C. The regression line shows therelationship extracted in the low-B₁ regime for a related polymermaterial, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene](MEH-PPV). To demonstrate the quality of the data, the differentialcurrent recorded on resonance at B₁=52(1) μT is plotted in FIG. 4D. Thespectrum is accurately described by the sum of two Gaussian functions(the largest peak), with the two Gaussians (middle peak and small broadpeak). The two Gaussians arise from the hyperfine-field distributionsexperienced by the electron and hole wave-functions in the polymer,respectively.

In examining the dependence of resonance spectrum on B₁ strength, one ofthe biggest challenges lies in accurately determining the magnitude ofB₁. This parameter can neither be measured directly with an externaldetector, since the RF stripline does not radiate—the resonance effectis generated in the near-field of the stripline; nor can it becalculated accurately, since the stripline invariably suffers fromreflection and coupling losses and the local field is highlyinhomogeneous. In time-resolved electrically detected magnetic resonanceexperiments, B₁ can be determined from the Rabi precession frequency.Here, the effect of power broadening on the resonance spectrum isexamined to determine the magnitude of B₁. Power broadening gives thespectrum the shape of a Lorentzian curve, whereas the underlyingstatistical distribution of local hyperfine fields experienced by eachspin follows a Gaussian shape, with each carrier species being describedby a distinct Gaussian curve. At low driving powers, the hyperfinedisorder dominates the spectrum so that a pure double-Gaussian shapeemerges as shown in FIG. 4D. As the power increases, the spectral shapechanges gradually from double-Gaussian to Lorentzian, with intermediatefields showing a spectrum consisting of a convolution of the two, adouble-Voigt line. FIG. 5 shows examples of resonance spectra recordedat different RF excitation powers, with the power increasing from top tobottom. The spectra clearly broaden with increasing power. Using aglobal fitting procedure for all data with only the two hyperfinedistributions of electron and hole spin along with B₁ as the threefitting parameters for all data sets, a precise value of B₁ can beassigned to each resonance spectrum.

The fitting procedure was performed as follows. In the low radiofrequency (RF) driving power regime, the electron spin resonancelinewidth of charge carriers in organic semiconductors are welldescribed by two Gaussian functions with equal centers at a Landé-factorat g˜2.023, whose different widths correspond to the distributions ofproton induced hyperfine fields experienced by electron polarons andhole polarons, respectively. As the driving power increases the effectof power broadening, the electrically detected magntic resonance (EDMR)lines eventually both assumed a Lorentzian shape governed by thestrength of the driving field B₁ (the full width at half maximum will beequal 2B₁). In the intermediate power regime, when both power broadeningand the inhomogeneity caused by the hyperfine fields are significant aconvolution of a Gaussian and a Lorentzian function, the so called Voigtfunction described the polaron resonances appropriately.

For the fit of the polaron pair EDMR lines presented here, double Voigtfunctions

$y = {{A\frac{2{\ln(2)}}{\pi^{3}/2}\frac{w_{L}}{w_{G\; 1}^{2}}{\int_{- \infty}^{\infty}{\frac{e^{- t^{2}}}{\left( {\sqrt{\ln 2}\frac{w_{L}}{w_{G\; 1}}} \right)^{2} + \left( {{\sqrt{4{\ln(2)}}\frac{x - x_{c\; 1}}{w_{G\; 1}}} - t} \right)^{2}}\ {dt}}}} + {\frac{2{\ln(2)}}{\pi^{3}/2}\frac{w_{L}}{w_{G\; 2}^{2}}{\int_{- \infty}^{\infty}{\frac{e^{- t^{2}}}{\left( {\sqrt{\ln\; 2}\frac{w_{L}}{w_{G\; 2}}} \right)^{2} + \left( {{\sqrt{4{\ln(2)}}\frac{x - x_{c\; 2}}{w_{G\; 2}}} - t} \right)^{2}}\ {dt}}}}}$were used. Here, x_(c1) and x_(c22) are the centers of the resonancelines and R is the ratio between the resonance line intensities A of thefirst resonance line and A/R of the second resonance line. The Gaussianwidths of the two Voigt functions are w_(G1), w_(G2), respectively,while only one common Lorentzian w_(L) is needed since power broadeningis identical for all paramagnetic centers that are exposed to the sameradiation field. Since w_(L)=c√{square root over (p)}, where p is the RFpower applied by the thin film wire and 2B₁=w_(L). The error in B₁ isdetermined by the error of the conversion factor c, that resulted fromthe fit procedure.

Given the large number of fit parameters in the EDMR fit functionprovided above, the line width was measured repeatedly for variousapplied RF powers. The resulting data sets, as shown in the FIG. 5, werefit globally, i.e. the function given above was applied simultaneouslyto all obtained data sets while only the power variable p was changed.

With accurate values of B₁ extracted for a given power, the effect ofdriving field strength on the resonance spectrum was investigated. Thespin states responsible for magnetic resonance change as the drivingfield is raised from the weak-coupling low-field (perturbative) to theultrastrong-coupling high-field regime. FIG. 6A summarizes the twolimits. In the perturbative regime, the driving field B₁ is much smallerthan the average difference in the distribution of hyperfine fieldsexperienced by the two charge carriers, δB_(hyp). This field lifts thedegeneracy between the antisymmetric pair states of triplet and singletsymmetry, T₀ and S₀. Magnetic resonance transitions then occur to thepure triplet states T₊ and T⁻. In contrast, when B₁ is of the order ofor larger than δB_(hyp), the approximation of pure single-spin statesbreaks down. Three new triplet superposition states emerge as stated inFIG. 6A, besides the pure singlet state. However, the selection rulesfor allowed magnetic resonance transitions change. Transitions betweensinglet and triplet are blocked and only occur between the three newsuperposition triplet levels. This change of basis set is a consequenceof indistinguishability of the spin pair with respect to the drivingelectromagnetic field: once the driving field strength exceedsinhomogeneous broadening, which arises predominantly from the localhyperfine fields, the individual spins of the pairs become quantummechanically indistinguishable, necessitating a description in terms ofa new common wavefunction. This phenomenon is a manifestation of theDicke effect, which is best known from superradiant luminescence ofatomic gases, and has a profound effect on the magnetic resonanceamplitude and spectrum. FIG. 6B plots the normalized device currentchange ΔI as a function of B₀ and B₁ on a false-color scale. The maximalresonance amplitude is shown in FIG. 6C. Initially, the overallamplitude, which is negative since it measures current quenching, riseswith increasing B₁ but then saturates around B₁=0.2 mT. Subsequently,the resonance amplitude decreases again, until the resonance vanishescompletely at B₁=1.1 mT. Subsequently, the resonance inverts and showsthe same effect of power broadening as seen for very low B₁ fields, butwith reversed sign.

Previous exploration of this exotic regime of magnetic resonance wasprobed in a similar conjugated polymer, MEH-PPV, with devices mounted inan external RF coil to generate the high B₁ fields. This approachrequires very high driving powers for the coils and leads to heating ofthe device and, ultimately, catastrophic breakdown: the coils simplyevaporate and the OLED overheats. Notably, for B₁ fields generated withcoils around devices of MEH-PPV, which has a comparable hyperfinecoupling strength to SY-PPV, the inversion of the resonance sign was notdemonstrated to signify the emergence of the Dicke regime. Thistransition is now clearly resolved in the new data in FIGS. 6A-6C.Nevertheless, up to a field of B₁=1.2 mT, the MEH-PPV data closelyfollow those acquired here for SY-PPV. The comparison between the twomeasurements is important, since it demonstrates the accuracy of the B₁calibration carried out here. The coils used in the earlier experimentcould be pulsed, so that Rabi oscillations could be measured directly inthe time domain, providing an absolute measure of B₁. Finally, it isnoted that the measurement technique is highly sensitive to potentialheating effects arising from the stripline, since these would lead to achange of the current-voltage characteristic, which is recorded forevery B₁ field. There does not appear to be any change of the I-Vcharacteristics with B₁ off resonance, implying that, in the field rangestudied here, heating effects can be neglected.

Example 4

This example illustrates fabrication of monolithic copper-basedlithographically defined wires for broadband (low-Q) EPR excitationlocated 1 micron beneath organic light emitting diode (OLED) stacks witha circular surface area of 57 μm diameter that will allow for high B₁and low B₀ EDMR spectroscopy. For the fabrication of these integratedresonator/OLED devices, we deposited crossed wires on top of a quartzsubstrate, followed by the deposition of a 1 micron thick dielectricinsulator stack below an OLED back contact. These template structureswhere brought into an inert glovebox environment where the OLED devicelayers were deposited.

A monolithic spintronic device was fabricated similar to Example 2. Inthis example, the starting substrate was quartz instead of Si/SiN (FIG.1). 1 μm thick copper wires were fabricated to induce a B₁ fieldunderneath OLED back contact Ti/Ag/Ti layers. Layers of SiN, SiO₂ andspin-on-glass (SOG) with a total thickness of more than 1 μm were usedas insulation. FIG. 7 is graph of current as a function of voltage forthe formed device.

DC magnetoresistance in the OLED was measured by detecting changes indevice current while sweeping the magnetic field B₀ as reported in FIG.8A-8C. Magnetic resonance (MR) was induced by applying RF field tomicrowire. In order to determine B₁, we measured the inhomogenouslypower-broadened magnetic resonance line width ΔBi for various RF powersP, and determined the natural line width ΔBn and the conversion factor Cnumerically as shown in FIG. 8D.

The integrated devices allow for EDMR spectroscopy over broad frequencyranges with high driving field B₁ to square-root-of-power ratios as wellas thin film induced magnetic field modulation. In the RF range (f˜100MHz) the structures allow for the continuous-wave application of B₁>1 mTwithout any recognizable heating effect and without the use of RFamplifiers (<50 mW produce B₁>1.2 mT). These structures can be used notjust for magnetometry but also for non-linear EDMR spectroscopy at highB1 and low frequency/B₀ conditions.

Example 5

A monolithic spintronic device was formed in a similar manner toExamples 2 and 4, with the configuration shown in FIG. 9A to operate asa magnetometer, including the 50 nm SiO₂ layer as an adhesion layerwhich has insulating properties. In this configuration the thin filmwire is formed on the silicon substrate in a U-shape. This allowscontact pads to be oriented on a common side of the device. Similarly,the thin-film device was formed in the active area and having a largerexposed contact pad. This configuration can be particularly useful forvery high excitation power. The positions of RF contacts and samplecontacts are well separated to avoid possible cross-talk between thewires that connects to these contacts. The shape of the wires can alsobe varied as desired and this design is one possible example.

FIG. 9B shows observed Bloch Siegert shift in this configuration wherethe organic semiconductor material is a fully deuterated MEH-PPV, withmuch lower hyperfine that results in narrow resonance line width whichalso results in increasing the sensitivity of the magnetometer. Thisplot is of raw data of magnetoconductivity curves as a function ofdriving power at 85 MHz, plotted on a false color scale, showing powerbroadening of the resonance, bleaching and a subsequent inversion ofresonance sign at high driving fields. Furthermore, this plot clearlyshows a Block Siegert shift (black line and lower red line) which hasnot been previously experimentally observed.

FIG. 9C is a plot of current as a function of voltage for the example ofFIG. 9A.

FIG. 9D is a plot of raw data from a magnified portion of FIG. 9B.

FIG. 9E is a plot of the amplitude of the resonance maximum at 3.07 mTas a function of B₁ compared to results obtained with a differentconjugated polymer material, MEH-PPV, in an OLED driven by a coil ratherthan a stripline for the example of FIG. 9A. Notably, the scale fordeuterated (black) is 2.5 times that shown in the y-axis labels which isscaled for the fully deuterated (FD) data. This also illustrates thathyperfine field for fully deuterated based devices are 2.5 times lowerthan deuterated devices.

FIG. 9F is an exploded view of a portion of data from FIG. 9E.

The foregoing detailed description describes the invention withreference to specific exemplary embodiments. However, it will beappreciated that various modifications and changes can be made withoutdeparting from the scope of the present invention as set forth in theappended claims. The detailed description and accompanying drawings areto be regarded as merely illustrative, rather than as restrictive, andall such modifications or changes, if any, are intended to fall withinthe scope of the present invention as described and set forth herein.

What is claimed is:
 1. A monolithic reusable microwire assembly,comprising: a substrate; an electrically conductive thin-film wireformed on the substrate, said thin film wire having a narrow segmentforming an active area; a thermally and electrically insulating barrierformed on the electrically conductive thin-film wire; aroughness-reducing layer formed on the thermally and electricallyinsulating barrier, said roughness-reducing layer having a surfaceroughness of less than or equal to 20 nm; and a substrate adhesionlayer, a thin film wire adhesion layer, a diffusion barrier layer, or acombination thereof formed between the substrate and the thin film wire.2. The monolithic reusable microwire assembly of claim 1, wherein thesubstrate comprises silicon, quartz, glass, plastic, or a combinationthereof.
 3. The monolithic reusable microwire assembly of claim 1,wherein the substrate is not thermally isolated from the thin film wireand functions as a heat drain for the thin film wire.
 4. The monolithicreusable microwire assembly of claim 1, wherein the substrate adhesionlayer comprises SiO₂.
 5. The monolithic reusable microwire assembly ofclaim 1, wherein the thin film wire adhesion layer comprises titanium orchromium.
 6. The monolithic reusable microwire assembly of claim 1,wherein the diffusion barrier layer comprises SiN.
 7. The monolithicreusable microwire assembly of claim 1, wherein the thin film wirecomprises at least one of copper, aluminum, chromium, and niobium. 8.The monolithic reusable microwire assembly of claim 1, furthercomprising an adhesion layer, an etch stop layer, or a combinationthereof positioned between the thin film wire and the thermally andelectrically insulating barrier.
 9. The monolithic reusable microwireassembly of claim 8, wherein the adhesion layer comprises titanium,wherein the etch stop layer comprises at least one of gold, silver andplatinum, and wherein the thermally and electrically insulating barriercomprises a SiN layer, a SiO₂ layer, or a combination thereof.
 10. Themonolithic reusable microwire assembly of claim 1, wherein theroughness-reducing layer has a surface roughness of less than or equalto 20 nm.
 11. A monolithic spintronic device, comprising, a monolithicreusable microwire assembly, comprising: a substrate; an electricallyconductive thin-film wire formed on the substrate, said thin film wirehaving a narrow segment forming an active area; a thermally andelectrically insulating barrier formed on the electrically conductivethin-film wire; and a roughness-reducing layer formed on the thermallyand electrically insulating barrier, said roughness-reducing layerhaving a surface roughness of less than or equal to 20 nm; and a thinfilm device formed on the monolithic reusable microwire assembly to formthe monolithic spintronic device, and wherein the thin-film device ispositioned directly above the active area of the thin film wire.
 12. Themonolithic spintronic device of claim 11, wherein the thin-film deviceis at least one of an organic light-emitting diode (OLED), lightemitting diode, magnetometer, solar cell, resistor, and capacitor. 13.The monolithic spintronic device of claim 12, wherein the OLED comprisesa hole injector layer and an emitting layer.
 14. The monolithicspintronic device of claim 13, wherein the hole injector layer comprisespoly(styrene-sulfonate)-doped poly(3,4-ethylenedioxythiophene)(PEDOT:PSS) and wherein the emitting layer comprises at least one ofsuper-yellow poly(phenylene-vinylene) (SY-PPV), MEH-PPV (partially andfully deuterated), PCBM, P₃HT, Alq₃, amorphous silicon, SiC andPEDOT:PSS.
 15. The monolithic spintronic device of claim 11, wherein thethin film device has a width of from 20 nm to 400 nm.
 16. The monolithicspintronic device of claim 11, further comprising a cathode formed onthe thin film device.
 17. The monolithic spintronic device of claim 11,further comprising an electrical contact layer formed between thethin-film device and the monolithic thin-film microwire assembly.
 18. Amethod of manufacturing a monolithic microwire assembly, comprising:depositing an electrically conductive thin film microwire on asubstrate; shaping the thin film microwire to have a narrow segmentforming an active area of the thin film microwire; and depositing anelectrical and thermal insulation barrier on the thin film microwire;depositing a roughness-reducing layer on the electrical and thermalinsulation barrier to achieve a surface roughness of less than 5 nm. 19.The method of claim 18, further comprising forming an oxide layer on thesubstrate prior to depositing the electrically conductive thin filmmicrowire on the substrate.
 20. The method of claim 19, furthercomprising depositing a diffusion barrier layer on the oxide layer priorto depositing the electrically conductive thin film microwire on thesubstrate.
 21. The method of claim 20, wherein the diffusion barrierlayer comprises SiN.
 22. The method of claim 20, further comprisingdepositing a thin film microwire adhesion layer on the diffusion barrierlayer.
 23. The method of claim 22, wherein the thin film microwireadhesion layer comprises titanium.
 24. The method of claim 18, furthercomprising depositing a thin film microwire adhesion layer on the thinfilm microwire.
 25. The method of claim 18, further comprisingdepositing an etch stop layer on the thin film microwire or interveningthin film microwire adhesion layer prior to shaping the thin filmmicrowire.
 26. The method of claim 25, further comprising depositing anetch stop adhesion layer on the etch stop layer.
 27. The method of claim18, wherein shaping the thin film microwire comprises photolithography,wet etching, or a combination thereof.
 28. The method of claim 18,further comprising etching an exposed surface of the electrical andthermal insulation barrier to reduce surface roughness to less than orequal to a thickness of the top layer.